U.S. patent application number 11/719711 was filed with the patent office on 2008-07-24 for extruded propylene resin foam.
Invention is credited to Yasuhiko Otsuki, Minoru Sugawara, Ryoichi Tsunori.
Application Number | 20080176971 11/719711 |
Document ID | / |
Family ID | 36407250 |
Filed Date | 2008-07-24 |
United States Patent
Application |
20080176971 |
Kind Code |
A1 |
Sugawara; Minoru ; et
al. |
July 24, 2008 |
Extruded Propylene Resin Foam
Abstract
An object of the present invention is to provide an extruded
propylene-based resin foam in which a average diameter of cells
therein can be reduced while a high expansion ratio remains high,
thereby providing an excellent insulation efficiency. The extruded
propylene-based resin foam according to the present invention is
extruded propylene-based resin foam that is formed by
extrusion-foaming a propylene-based resin, and the extruded
propylene-based resin foam has the expansion ratio of 10 or more
and the average cell diameter of less than 400 .mu.m. With this
configuration, the extruded foam can have a plurality of air bubble
walls therein. Thus, the extruded propylene-based resin foam can
efficiently block external radiant heat, thereby realizing
excellent insulation efficiency.
Inventors: |
Sugawara; Minoru; (Chiba,
JP) ; Otsuki; Yasuhiko; (Chiba, JP) ; Tsunori;
Ryoichi; (Chiba, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Family ID: |
36407250 |
Appl. No.: |
11/719711 |
Filed: |
November 18, 2005 |
PCT Filed: |
November 18, 2005 |
PCT NO: |
PCT/JP2005/021281 |
371 Date: |
May 18, 2007 |
Current U.S.
Class: |
521/145 |
Current CPC
Class: |
C08J 9/122 20130101;
C08J 2323/12 20130101; Y02P 20/582 20151101; C08F 110/06 20130101;
Y10T 428/1352 20150115; C08J 2205/052 20130101; C08J 2201/03
20130101; C08F 210/06 20130101; C08F 2500/12 20130101; C08F 2500/11
20130101; C08F 2500/15 20130101; C08F 2500/11 20130101; C08F
2500/12 20130101; C08F 210/06 20130101; C08J 2203/08 20130101; C08F
10/06 20130101; C08F 110/06 20130101; C08F 2500/15 20130101 |
Class at
Publication: |
521/145 |
International
Class: |
C08F 10/06 20060101
C08F010/06 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 19, 2004 |
JP |
2004-336679 |
Claims
1. An extruded propylene-based resin foam that is formed by
extrusion-foaming a propylene-based resin, the extruded
propylene-based resin foam having: an expansion ratio of 10 or
more; and an average cell diameter of less than 400 .mu.m.
2. The extruded propylene-based resin foam according to claim 1,
wherein a closed cell content is 40 or more %.
3. The extruded propylene-based resin foam according to claim 1,
wherein the average cell diameter is 200 .mu.m or less.
4. The extruded propylene-based resin foam according to claim 1,
wherein the extruded propylene-based resin foam is an assembly of
bundled threads of an extruded foam in which a plurality of
extrusion-foamed threads are bundled.
5. The extruded propylene-based resin foam according to claim 1,
wherein the propylene-based resin constituting the extruded foam is
a propylene-based multistage polymer made of the following
constituents (A) and (B): (A) a constituent containing a propylene
homopolymer component having a intrinsic viscosity [.eta.] of more
than 10 dL/g, which is measured in a tetralin solvent at
135.degree. C. or a copolymer component of propylene and
.alpha.-olefin having carbon number of 2 to 8, the component
occupying 5 to 15 mass % of the total polymer; and (B) a
constituent containing a propylene homopolymer component having a
intrinsic viscosity [.eta.] of 0.5 to 3.0 dL/g, which is measured
in a tetralin solvent at 135.degree. C. or a copolymer component of
propylene and .alpha.-olefin having carbon number of 2 to 8, the
component occupying 85 to 95 mass % of the total polymer.
6. The extruded propylene-based resin foam according to claim 5,
wherein a relationship between a melt flow rate (MFR) at
230.degree. C. and a melt tension (MT) at 230.degree. C. of the
propylene-based multistage polymer has satisfies the following
expression (I): log(MT)>-1.33 log(MFR)+1.2 (I)
7. The extruded propylene-based resin foam according to claim 1,
wherein the propylene-based resin constituting the extruded foam is
a propylene-based multistage polymer made of the following
constituents (A) and (B): (A) a constituent containing a propylene
homopolymer component having a intrinsic viscosity [.eta.] of more
than 10 dL/g which is measured in a tetralin solvent at 135.degree.
C. or a copolymer component of propylene and .alpha.-olefin having
carbon number of 2 to 8, the component occupying 5 to 20 mass % of
the total polymer; and (B) a constituent containing a propylene
homopolymer component having a intrinsic viscosity [.eta.] of 0.5
to 3.0 dL/g, which is measured in a tetralin solvent at 135.degree.
C. or a copolymer component of propylene and .alpha.-olefin having
carbon number of 2 to 8, the component occupying 80 to 95 mass % of
the total polymer.
8. The extruded propylene-based resin foam according to claim 5,
wherein a relationship between a melt flower rate (MFR) at
230.degree. C. and a melt tension (MT) at 230.degree. C. of the
propylene-based multistage polymer satisfies the following equation
(I): log(MT)>-1.33 log(MFR)+1.2 (I)
Description
TECHNICAL FIELD
[0001] The present invention relates to extruded propylene-based
resin foam having an excellent insulation efficiency due to a high
expansion ratio and a small average cell diameter.
BACKGROUND ART
[0002] Extruded foam molded by extrusion-foaming a thermoplastic
resin and an assembly of bundled threads of the extruded foam
molded by a so-called strand-extrusion involving the steps of
extruding the thermoplastic resin from dies having a large number
of small pores; bundling extruded resin threads together; and
fusing and foaming the surfaces thereof are excellent in mechanical
properties even though light in weight. Therefore, the foam is
broadly applied as structural materials in various fields, such as
the fields of building construction, civil engineering and the
fields of automobiles, in particular, employed as thermal
insulating materials. As such extruded foam of a thermoplastic
resin extruded foam formed of polyurethane-based resins or
polystyrene-based resins is known.
[0003] However, a polyurethane resin and a polystyrene resin are
materials that are not always excellent in recycling
characteristics, and there is a problem that when these resins are
used, it is difficult to sufficiently comply with the construction
recycling law (law on recycling of materials for construction
works, etc.). In addition, the polystyrene resin has poor heat
resistance and chemical resistance. Therefore extruded foam made of
a thermoplastic resin that is alternative to those resins has been
demanded.
[0004] On the other hand, a polypropylene-based resin, which is
excellent in mechanical property, heat-resisting property chemical
resistance, electrical property and the like, is also a low cost
material, so that it is widely used in various molding fields.
Thus, extruded foam of the polypropylene-based resin is also
expected to have high industrial utility. However when melted,
polypropylene, which is a linear polymer resin, may decrease the
strength as a result of a drastic decrease in viscosity, and
consequently the resin hardly holds the air bubbles of foam and
foam braking can easily occur. Therefore, it is difficult to obtain
extruded foam having as high a closed cell content air bubbles and
high an expansion ratio as those of the conventional thermoplastic
resins. In addition, it is difficult to uniform and densify the
diameters of the foam cells (air bubbles) of the extruded molded
product. Therefore, an improvement in moldability has been
desired.
[0005] Here, insulation efficiency in a case that the extruded foam
is used as a thermal insulation material depends on both the
expansion ratio and the cell diameter at a certain range of
expansion ratio (for example, 10 or more). In other words, a higher
expansion ratio leads to an enhanced insulation efficiency because
the thinner a material wall is, the smaller a heat-transfer amount
is. Similarly, when the cell diameter is reduced with the same
expansion ratio, the number of cell walls blocking radiant heat
increase, so that less heat is conducted, thereby improving heat
insulation properties. Accordingly, the smaller cell diameter is
preferred. As described above, in a state where expansion ratio is
made high, when an average cell diameter is made small to improve
the heat insulation efficiency a thickness of molded product can be
reduced, which also brings an additional effect of cost reduction.
Therefore, notwithstanding the difficulty of the moldability as
described above, there has been a need of an improved expansion
ratio and a decreased cell diameter.
[0006] Under such a circumstance, researches have been carried out
to improve the expansion ratio and reduce the cell diameter of the
extruded propylene-based resin foam. For example, there is provided
an assembly of bundled threads of extruded foam made of a
polypropylene-based resin (i.e., a structural material of the resin
foam), the structural material having a biaxial extensional
viscosity of 3.times.10.sup.6 poises or more and a biaxial strain
hardening rate of 0.25 or more at a biaxial extensional strain of
0.2 and (see, Patent Document 1). In addition, there is also
provided an assembly of bundled threads of an extruded foam
obtained through steps of melt-kneading a mixture of a
predetermined polypropylene-based resin and a foaming agent in an
extruder; extrusion-foaming the mixture from the extrusion die
having a plurality of small pores to be formed into threads under
low-temperature and low-pressure conditions after the temperature
is adjusted suitably for foaming; and transferring the threads into
a cylindrical device for bundling and fusing while the threads of
the foam is softened (see, for example, Patent Document 2).
[0007] [Patent Document 1] JP 09-25354 A
[0008] [Patent Document 2] JP 2001-1384 A
DISCLOSURE OF INVENTION
Problems to be Solved by the Invention
[0009] However, although such a conventional extruded
propylene-based resin foam as disclosed in the above-mentioned
patent documents can provide an improvement of expansion ratio to
some extent, it is difficult to reduce the average cell diameter to
less than 400 .mu.m. Thus, the difficulty has been impeditive to a
further improvement in the insulation efficiency.
[0010] Therefore, it is an object of the present invention to
provide extruded propylene-based resin foam in which an average
diameter of cells therein can be reduced while a high expansion
ratio remains high, thereby providing an excellent insulation
efficiency.
Means for Solving the Problems
[0011] In order to achieve the above-mentioned object, the extruded
propylene-based resin foam according to an aspect of the present
invention is extruded propylene-based resin foam that is formed by
extrusion-foaming a propylene-based resin, the extruded
propylene-based resin foam having: an expansion ratio of 10 or
more; and an average cell diameter of less than 400 .mu.m.
[0012] The extruded propylene-based resin foam according to the
aspect of the present invention has the expansion ratio of 10 or
more and the average cell diameter (air bubble diameter) of less
than 400 .mu.m, so that a large number of air bubble walls can be
formed in the extruded foam, thereby efficiently blocking radiation
heat from the outside. As a result, extruded foam excellent in
insulation efficiency can be provided.
[0013] A propylene-based resin constituting the extruded foam has
not only an excellent recycling performance, but also a favorable
chemical resistance, heat-resistance, and the like. Accordingly,
the extruded propylene-based resin foam according to the present
invention also has such properties (recycling performance, chemical
resistance, and heat-resistance). Further, the use of the
propylene-based resin that is a low cost material makes it possible
to provide extruded foam having the above-mentioned effects at low
cost.
[0014] In the extruded propylene-based resin foam according to the
aspect of the present invention, a closed cell content is
preferably 40 or more %.
[0015] According to this aspect of the present invention, the
extruded propylene-based resin foam has an independent foam rate of
40 or more % so that a large number of air bubbles prevent the heat
from being transferred. Thus, the extruded foam has an enhanced
insulation efficiency, excellent mechanical strengths such as an
impact strength, and an excellent moisture resistance.
[0016] In the extruded propylene-based resin foam according to the
aspect of the present invention the average cell diameter is
preferably 200 .mu.m or less.
[0017] According to this aspect of the present invention, the
extruded propylene-based resin foam has the average cell diameter
is further reduced to 200 .mu.m or less, so that more air bubble
walls can be formed in the extruded foam. Therefore, the extruded
foam has more excellent insulation efficiency.
[0018] The extruded propylene-based resin foam according to the
aspect of the present invention is preferably an assembly of
bundled threads of an extruded foam in which a plurality of
extrusion-foamed threads are bundled.
[0019] According to this aspect of the present invention, the
extruded propylene-based resin foam is formed as an assembly of
bundled threads where a large number of threads of the extruded
foam are bundled together. Accordingly, the expansion ratio of the
extruded foam can be enhanced. Therefore, it is easy to mold a
molded foam product having a high expansion ratio and a sufficient
thickness in various forms.
[0020] In the extruded propylene-based resin foam according to the
aspect of the present invention, the propylene-based resin
constituting the foam is preferably a propylene-based multistage
polymer made of the following constituents (A) and (B): (A) a
constituent containing a propylene homopolymer component having a
intrinsic viscosity [.eta.] of more than 10 dL/g, which is measured
in a tetralin solvent at 135.degree. C. or a copolymer component of
propylene and a-olefin having carbon number of 2 to 8, the
component occupying 5 to 15 mass % of the total polymer; and
(B) a constituent containing a propylene homopolymer component
having a intrinsic viscosity [.eta.] of 0.5 to 3.0 dL/g, which is
measured in a tetralin solvent at 135.degree. C. or a copolymer
component of propylene and a-olefin having carbon number of 2 to 8,
the component occupying 85 to 95 mass % of the total polymer.
[0021] The propylene-based multistage polymer is a linear
propylene-based polymer having a higher melt tension due to the
addition of the constituent (A) that is an
ultrahigh-molecular-weight propylene based polymer. The multistage
polymer also has an excellent viscoelastic property because the
viscoelasticity is adjusted by controlling a molecular weight
distribution.
[0022] Therefore, by using the propylene-based multistage polymer
having the excellent viscoelastic property as the constituent
material, the extruded propylene-based resin foam can reliably has
the expansion ratio of 10 or more, the average cell diameter of
less than 400 .mu.m (preferably 200 .mu.m or less). In addition,
according to the propylene-based multistage polymer, the closed
cell content in the extruded foam can be increased. For example,
the closed cell content of 40 or more % car be surely attained.
[0023] In the extruded propylene-based resin foam according to the
aspect of the present invention, a relationship between a melt flow
rate (MFR) at 230.degree. C. and a melt tension (MT) at 230.degree.
C. of the propylene-based multistage polymer preferably satisfies
the following expression (I):
[0024] [Formula 1]
log(MT)>-1.33 log(MFR)+1.2 (1)
[0025] According to this aspect of the present invention, the
relationship between the melt flow rate (MFR) at 230.degree. C. and
the melt tension (MT) at 230.degree. C. is represented by the
above-mentioned expression (I). Therefore, molding of a
foam-molding having the high expansion ratio can be realized, and
the extruded foam can easily and reliably have the expansion ratio
of 10 or more.
BEST MODE FOR CARRYING OUT THE INVENTION
[0026] The extruded propylene-based resin foam according to the
present invention (hereinafter referred to as extruded foam) is
provided by extrusion-foaming a propylene-based resin, and has the
expansion ratio of 10 or more and the average cell diameter of less
than 400 .mu.m. With this arrangement, the extruded foam having the
excellent insulation efficiency can be provided.
[0027] In addition, when the extruded foam has the closed cell
content of 40 or more preferably 60 or more %, a large number of
independent air bubbles substantially prevents heat from being
transferred. Therefore, the extruded foam has the further advanced
insulation efficiency, excellent mechanical strengths such as
impact strength, and excellent moisture resistance.
[0028] As the propylene-based resin forming the extruded foam of
the present invention configured as described above, any
propylene-based resin having high melt tension when melted can be
used. For example, any of those described in JP 10-279632 A, JP
2000-309670 A, JP 2000-336198 A, JP 2002-12717 A, JP 2002-542360 A,
and JP 2002-509575 A can be used.
[0029] Further, as described above, for obtaining the extruded foam
of the present invention, it is preferable, to increase the melt
tension of the resin at the time of melting and to use as the
polypropylene-based resin a resin material having excellent
viscoelastic property.
[0030] As an example of the propylene-based resin having excellent
viscoelastic property as described above, it is advantageous to use
as the a propylene-based resin constituting a foam a
propylene-based multistage polymer including constituents (A) and
(B) as described below:
[0031] (A) a constituent containing a propylene homopolymer
component having a intrinsic viscosity [.eta.] of more than 10
dL/g, which is measured in a tetralin solvent at 135.degree. C. or
a copolymer component of propylene and a-olefin having carbon
number of 2 to 8, of the component occupying 5 to 20 mass % of the
total polymer; and
[0032] (B) a constituent containing a propylene homopolymer
component having a intrinsic viscosity [.eta.] of 0.5 to 3.0 dL/g,
which is measured in a tetralin solvent at 135.degree. C. or a
copolymer component of propylene and a-olefin having carbon number
of 2 to 8, the component occupying 80 to 95 mass % of the total
polymer.
[0033] The propylene-based multistage polymer is a linear
propylene-based polymer having a higher melt tension due to the
addition of the constituent (A) that is an
ultrahigh-molecular-weight propylene based polymer. The multistage
polymer also has a viscoelastic property adjusted by controlling a
molecular weight distribution. The use of such a propylene-based
multistage polymer having the excellent viscoelastic property as a
component material is preferable because the propylene-based
polymer meeting the requirements of the present invention as
described above (i.e. the expansion ratio of 10 or more, the
average cell diameter of less than 400 .mu.m (preferably 200 .mu.m
or less), and the closed cell content of 40 or more %) can be
reliably provided.
[0034] Now, the melt tension becomes insufficient when the
component (A) has a intrinsic viscosity of 10 dL/g or less. Thus,
the desired foaming performance may not be obtained.
[0035] In addition, when the mass fraction of the component (A) is
less than 5 mass %, the melt tension becomes insufficient and the
desired foaming performance may not be obtained. In contrast, when
the mass fraction exceeds 20 mass %, a so-called melt fracture may
intensify, which leads to a rough surface or the like of the
extruded foam and resulting in a decrease in product quality.
[0036] The intrinsic viscosity of the component (A) is preferably
more than 10 dL/g as described above, more preferably in the range
of 11 to 20 dL/g, and particularly preferably in the range of 13 to
18 dL/g.
[0037] In addition, the mass fraction of the component (A) is
preferably in the range of 8 to 18 mass %, and particularly
preferably in the range of 10 to 16 mass %.
[0038] The melt tension becomes insufficient when the intrinsic
viscosity of the component (B) is less than 0.5 dL/g and the
desired foaming performance may not be obtained. In contrast, when
it exceeds 3.0 dL/g, the viscosity becomes too high and a suitable
extrusion molding process may not be performed.
[0039] Further when the mass fraction of the component (B) is less
than 80 mass %, a preferable extrusion molding process may not be
easily performed. When the mass fraction exceeds 95 mass %,
likewise the melt tension becomes low and a preferable extrusion
molding process may not be easily performed.
[0040] As descried above the component (B) has a intrinsic
viscosity preferably in the range of 0.5 to 3.0 dL/g, more
preferably in the range of 0.8 to 2.0 dL/g and particularly
preferably in the range of 1.0 to 1.5 dL/g.
[0041] Further the mass fraction of the component (B) is preferably
in the range of 82 to 92 mass %, and particularly preferably in the
range of 84 to 90 mass %.
[0042] In this propylene-based multistage polymer, a-olefin having
carbon number of 2 to 8 as a constituent component of the copolymer
component, can be, for example, a-olefins other than propylene,
such as ethylene and 1-butene. Among them, it is preferable to use
ethylene.
[0043] In addition, the propylene-based multistage polymer has the
melt flow rate (MFR) at 230.degree. C. of preferably 100 g/10 min.
or less, and particularly preferably 20 g/10 min. or less. When MFR
exceeds 100 g/10 min., the melt tension and viscosity of the
multistage polymer become low, the molding can be made
difficult.
[0044] The propylene-based multistage polymer preferably has a
relationship between the melt flow rate (MFR) at 230.degree. C. and
the melt tension (MT) at 230.degree. C. represented by the
following expression (I).
[0045] [Formula 2]
log(MT)>-1.33 log(MFR)+1.2 (I)
[0046] Here, when the relationship between the melt flow rate (MFR)
at 230.degree. C. and the melt tension (MT) at 230.degree. C. does
not satisfy the above expression (I), it becomes difficult to
perform the molding process of the foam with high expansion ratio.
In such a case, the extruded foam having an expansion ratio of 10
or more may not be obtained. The constant (1.2) in the expression
is preferably 1.3 or more, particularly preferably 1.4 or more.
[0047] Further, in order for the propylene-based multistage polymer
to have the relationship represented by the expression (I), the
polymer may include 5 mass % of the component (A).
[0048] In the propylene-based multistage polymer, it is preferable
that as a dynamic viscoelasticity in a molten state (the
relationship between angular frequency .omega. and storage-modulus
G'), an inclination of storage modulus at a side of high
frequencies is more than a predetermined level. Specifically, the
ratio G'(10)/G'(1) of the storage modulus G'(10) at the angular
frequency of 10 rad/s to the storage modulus G'(1) at the angular
frequency of 1 rad/s is preferably 2.0 or more, and particularly
preferably 2.5 or more. When the ratio G'(10)/G'(1) is smaller than
2.0, the stability of the extruded foam may decrease when an
external deformation such as elongation is applied to the extruded
foam.
[0049] Similarly in the propylene-based multistage polymer, it is
preferable that as a dynamic viscoelasticity in a molten state, an
inclination of the storage modulus at a side of low frequencies is
less than a predetermined level. Specifically, the ratio
G'(0.1)/G'(0.01) of the storage modulus G'(0.1) at the angular
frequency of 0.1 rad/s to the storage modulus G'(0.01) at the
angular frequency of 0.01 rad/s is preferably 6.0 or less, and
particularly preferably 4.0 or less. When the ratio
G'(0.1)/G'(0.01) exceeds 6.0, the expansion ratio of the extruded
foam may not be easily enhanced.
[0050] The propylene-based multistage polymer can be produced by
polymerizing the propylene or copolymer-zing propylene with
a-olefin having carbon number of 2 to 8 in a polymerization
procedure including two or more stages, using olefin-polymerization
catalysts including the following components (a) and (b) or the
following components (a), (b), and (c):
[0051] (a) A solid catalyst component produced by processing
titanium trichloride produced by reducing titanium tetrachloride
with an organic aluminum compound by an ether compound and an
electron acceptor;
[0052] (b) An organic aluminum compound; and
[0053] (c) Cyclic ester compound.
[0054] In (a) the solid catalyst component produced by processing
the titanium trichloride produced by reducing the titanium
tetrachloride with the organic aluminum compound by the ether
compound and the electron acceptor (hereinafter, also simply
referred to as "(a) solid catalyst component"), as the organic
aluminum compounds to be used for reducing titanium tetrachloride,
there may be used, for example (i) alkyl aluminum dihalide,
specifically methyl aluminum dichloride, ethyl aluminum dichloride,
and n-propyl aluminum dichloride; (ii) alkyl aluminum sesquihalide,
specifically ethyl aluminum sesquichloride; (iii) dialkyl aluminum
halide, specifically dimethyl aluminum chloride, diethyl aluminum
chloride, di-n-propyl aluminum chloride, and diethyl aluminum
bromide; (iv) trialkyl aluminum, specifically trimethyl aluminum,
triethyl aluminum and triisobutyl aluminum; and (v) dialkyl
aluminum hydride, specifically diethyl aluminum hydride. Here, the
term "alkyl" refers to lower alkyl such as methyl, ethyl, propyl,
or butyl. In addition, the term "halide" refers to chloride or
bromide. Particularly the former is generally used.
[0055] The reduction reaction of the organic aluminum compound for
obtaining the titanium trichloride is generally performed at
temperatures ranging from -60 to 60.degree. C., preferably -30 to
30.degree. C. If the reduction reaction is performed at a
temperature of less than -60.degree. C., the reduction reaction
will require an extended period of time. In contrast, when the
reduction reaction is performed at a temperature of more than
60.degree. C., an excessive reduction may partially occur, which is
unfavorable. The reduction reaction is preferably performed under
the presence of an inactivated hydrocarbon solvent such as pentane,
heptane, octane, and decane.
[0056] Further, it is preferable to perform an ether treatment and
an electron acceptor treatment on the titanium trichloride obtained
by the reduction reaction of the titanium tetrachloride with the
organic aluminum compound.
[0057] Examples of ether compounds, which can be preferably used in
the ether treatment of the titanium trichloride, include ether
compounds in which each hydrocarbon residue is a chain hydrocarbon
having carbon number of 2 to 8, such as diethyl ether, di-n-propyl
ether, di-n-butyl ether, diisoamyl ether, dineopentyl ether,
di-n-hexyl ether, di-n-octyl ether, di-2-ethyl hexyl ether,
methyl-n-butyl ether, and ethyl-isobutyl ether. Among them in
particular, use of di-n-butyl ether is preferable.
[0058] Preferable examples of the electron acceptors that can be
used in the treatment of titanium trichloride include halogenated
compounds of elements in groups III to IV and VIII in the periodic
table, specifically, titanium tetrachloride, silicon tetrachloride,
boron trifluoride, boron trichloride, antimony pentachloride,
gallium trichloride, ferric trichloride, tellurium dichloride, tin
tetrachloride, phosphorus trichloride, phosphorus pentachloride,
vanadium tetrachloride and zirconium tetrachloride.
[0059] The treatment of titanium trichloride with the ether
compound and the electron acceptor in preparation of solid catalyst
component (a) may be performed using a mixture of both treatment
agents, or may be performed using one of these treatment agents at
first and then the other afterward. Note that among them, the
latter is more preferable than the former: the treatment with the
electron acceptor after the treatment with ether is more
preferable.
[0060] Prior to the treatment with the ether compound and the
electron acceptor, the titanium trichloride is preferably washed
with hydrocarbon. The above-mentioned ether treatment with titanium
trichloride is performed such that the titanium trichloride is
brought into contact with the ether compound. The titanium
trichloride treatment with the ether compound is advantageous when
performed such that those two are brought into contact with each
other in the presence of a diluent. Examples of the diluent
preferably include inactivated hydrocarbon compounds such as
hexane, heptane, octane, decane, benzene, and toluene. A treatment
temperature in the ether treatment is preferably in the range of 0
to 100.degree. C. In addition although a time period for the
treatment is not specifically limited, the treatment is generally
performed in the range of 20 minutes to 5 hours.
[0061] An amount of the ether compound used may be generally 0.05
to 3.0 mol, preferably 0.5 to 1.5 mol per tool of the titanium
trichloride. It is not preferable that the amount of the ether
compound used is less than 0.05 mol because a sufficient increase
in stereo regularity of a polymer to be produced is impaired. On
the other hand, it is unfavorable that the amount of the ether
compound used exceeds 3.0 mol because yield can be decreased even
though stereo regularity of a polymer to be generated increases.
Note that the titanium trichloride treated with the organic
aluminum compound or the ether compound is a composition mainly
containing titanium trichloride. Further, as the solid catalyst
component (a), Solvay-type titanium trichloride may be preferably
used.
[0062] As the organic aluminum compound (b), the same organic
aluminum compound as described above may be used.
[0063] Examples of the cyclic ester compound (c) include
.gamma.-lactone, d-lactone, and e-lactone among them, e-lactone is
preferably used.
[0064] Further, the catalyst for olefin polymerization used in the
production of the propylene-based multistage polymer can be
obtained by mixing the components (a) to (c) as described
above.
[0065] For obtaining the propylene-based multistage polymer among
two-stage polymerization methods, it is preferable to polymerize
propylene or copolymerize propylene and a-olefin having carbon
number of 2 to 8 in the absence of hydrogen. Here, the term "in the
absence of hydrogen" means "substantially in the absence of
hydrogen", so that it includes not only the complete absence of
hydrogen but also the presence of a minute amount of hydrogen (for
example, about 10 molppm). In short, the term "in the absence of
hydrogen" includes a case of containing hydrogen in an amount small
enough to prevent the intrinsic viscosity [.eta.] of the
propylene-based polymer or of the propylene-based copolymer at the
first stage, which is measured in a tetralin solvent at 135.degree.
C., from becoming 10 dL/g or less.
[0066] In the absence of hydrogen as described above, the
polymerization of propylene or the copolymerization of propylene
with a-olefin may result in the production of component (A) of the
propylene-based multistage polymer as a ultrahigh-molecular-weight
propylene-based polymer. The component (A) may be preferably
produced by slurry polymerization of a raw material monomer in the
absence of hydrogen at a polymerization temperature of preferably
20 to 80.degree. C. more preferably 40 to 70.degree. C., with a
polymerization pressure of generally ordinary pressure to 1.47 MPa,
preferably 03.9 to 1.18 MPa.
[0067] In addition, in this production method, the component (B) of
the propylene-based multistage polymer may be preferably produced
at the second stage or later. There is no specific limitation for
the production conditions of the component (B) except for a
limitation that the olefin-based polymer catalyst as described
above should be used. However, the component (B) may be preferably
produced by polymerizing a raw material monomer in the presence of
hydrogen serving as a molecular weight modifier at a polymerization
temperature of preferably 20 to 80.degree. C., more preferably 60
to 70.degree. C. with a polymerization pressure of generally
ordinary pressure to 1.47 MPa, preferably 0.19 to 1.18 MPa.
[0068] In the production method as described above, a preliminary
polymerization may be carried out before performing the present
polymerization. A powder morphology can be favorably maintained by
performing the preliminary polymerization. The preliminary
polymerization is generally performed such that propylene in amount
of preferably 0.001 to 100 g, more preferably 0.1 to 10 g per gram
of solid catalyst component is polymerized or copolymerized with
a-olefin having carbon number of 2 to 8 at a polymerization
temperature of preferably 0 to 80.degree. C. more preferably 10 to
60.degree. C.
[0069] Further, the propylene-based resin contained in the molding
material of the extruded foam may be a propylene-based resin
composition that includes the propylene-based multistage polymer as
described above and the propylene-based polymer having the melt
flow rate (MFR) at 230.degree. C. of 30 g/10 min. or less, and the
ratio M.sub.w/M.sub.n of weight average molecular weight (M.sub.w)
and a number average molecular weight (M.sub.n) of 50 or less.
[0070] The above-mentioned propylene-based multistage polymer may
be blended with other materials to provide a resin composition,
thereby improving the moldability and high-functionality of the
extruded foam, lowering the cost thereof, and the like.
[0071] The use of the resin composition allows the extruded foam to
have the high melt tension and the excellent viscoelastic property,
so that the extruded foam can be provided with the high expansion
ratio, good surface appearance, and an effect of preventing drawing
fracture at the time of sheet formation.
[0072] In the resin composition a weight ratio of the
propylene-based polymer to the propylene-based multistage polymer
is 6 to 1 or more, preferably 10 to 1 or more. If the weight ratio
is smaller than 8 to 1, the surface appearance of the extruded foam
may become poor.
[0073] The melt flow rate (MFR) of the propylene-based polymer is
preferably 30 g/40 min. or less, more preferably 15 g/10 min. or
less, particularly preferably 10 g/10 min. or less. When the MFR
exceeds 30 g/10 min., a defective molding of the extruded foam may
occur.
[0074] The M.sub.m/M.sub.n of the propylene-based polymer is
preferably 5.0 or less particularly preferably 4.5 or less. If the
M.sub.w/M.sub.n, exceeds 5.0, the surface appearance of the
extruded foam may be deteriorated.
[0075] Note that the propylene-based polymer can be produced by any
polymerization method using a known catalyst such as a
Ziegler-Natta catalyst or a metallocene catalyst.
[0076] As the dynamic viscoelasticity in a molten state (the
relationship between the angular frequency .omega. and the
storage-modulus G'), the resin composition preferably has a
predetermined level or more of the inclination of storage modulus
at high frequencies. In addition, the inclination of the storage
modulus at low frequencies is preferably a certain level or
less.
[0077] Specifically, the ratio G'(10)/G'(1) of the storage modulus
G'(10) at the angular frequency of 10 rad/s to the storage modulus
G'(1) at the angular frequency of 1 rad/s is preferably 5.0 or
more, more preferably 5.5 or more. When the ratio G'(10)/G'(1) is
smaller than 5.0, the stability of the extruded foam may decrease
when an external deformation such as elongation is applied to the
extruded foam.
[0078] In addition, the ratio G'(0.1)/G'(0.01) of the storage
modulus G'(0.1) at the angular frequency of 0.1 rad/s to the
storage modulus G'(0.01) at the angular frequency of 0.01 rad/s is
preferably 14.0 or less, particularly preferably 12.0 or less. When
the ratio G'(0.1)/G'(0.01) exceeds 14.0, the expansion ratio of the
extruded foam may not be easily increased.
[0079] Here, when the extruded foam is drawn, it is common that
components within a relaxation time of 1 to 10 sec leads to a
decrease in drawing property of the extruded foam. Thus, the larger
a contribution of the relaxation time of this region is, the
smaller the inclination of the storage modulus G'(1) becomes at the
angular frequency .omega. of about 1 rad/s. Thus, as an index of
the inclination, the ratio G'(10)/G'(1) of the storage modulus
G'(10) at the angular frequency .omega. of 10 rad/s is provided.
From the results of a numerical simulation and an experimental
analysis, it is found that the smaller the value is, the more
breakable foam at the time of drawing of the extruded foam is.
Therefore, the resin composition preferably has the G'(10)/G'(1) of
5.0 or more.
[0080] For foam breaking at the final stage of the growth of air
bubbles or foam breaking accompanying high-speed elongation
deformation near the die lips in the extrusion foam-molding
process, a certain degree of strain-hardness property is required.
Therefore, there is a need of an appropriate amount of the high
molecular weight component at an appropriate relaxation time field.
For that purpose, the storage modulus G' at the low-frequency
region needs to be large to some extent. Therefore, as the index,
the ratio G'(0.1)/G'(0.01) of the storage modulus G'(0.1) at the
angular frequency .omega. of 0.1 rad/s to the storage modulus
G'(0.01) at the angular frequency of 0.01 rad/s is provided. From
the results of a numerical simulation and an experimental analysis,
it is found that the larger the value is, the less the expansion
ratio becomes due to foam breaking. Therefore, the above-mentioned
resin composition preferably has the G'(0.1)/G'(0.01) of 14.0 or
less.
[0081] Further, as long as the effect of the present invention is
not prevented, where required, the propylene-based resin including
the resin composition and constituting the extruded foam of the
present invention may be added with any of stabilizers such as an
antioxidant, a neutralizer, a crystal-nucleus agent, a metal
deactivator, a phosphorus processing stabilizer, a UV absorbent, an
UV stabilizer, an optical whitening agent, a metallic soap, and an
antacid absorbent; and additives such as a cross-linking agent, a
chain transfer agent, a nucleating additive, a lubricant, a
plasticizer, a filler, an intensifying agent, a pigment, a dye, a
flame retardant, and an antistatic agent. The amounts of those
additives may be suitably determined depending on the
characteristic features and molding conditions, required in the
extruded foam to be molded.
[0082] When the propylene-based multistage polymer having the
excellent melting viscoelasticity as described above is used as the
propylene-based resin, the above-described additives can be added
to the polymer to be melt-kneaded together into a shape of pallet
by a conventionally-known melt-kneading machine in advance, and
thereafter, the desired extruded foam may be molded.
[0083] The extruded foam of the present invention can be obtained
by extrusion-foaming the above-mentioned propylene-based resin. A
known extrusion foam-molding device can be used as a production
device, in which a propylene-based resin is heated to be melted and
then kneaded with a suitable shearing stress applied thereto for
extrusion-foaming. An extruder included in the production device
may be either a uniaxial extruder or a biaxial extruder. As an
extrusion foam-molding device for example, an extrusion
foam-molding of a tandem-type disclosed in JP 2004-237729 A may be
used, to which two extruders are connected.
[0084] In addition, as method to foam the molded product, physical
foaming and chemical foaming may be adopted. In the physical
foaming, a fluid (gas) is injected into the molten resin material
at the time of molding, while in the chemical foaming, a foaming
agent is added to and mixed with the resin material.
[0085] In the physical foaming, the fluid to be injected may be
inert gas such as carbon dioxide (carbonic acid gas) and nitrogen
gas. In the chemical foaming, the foaming agent such as
azodicarbonamide and azobisisobutyronitrile may be used.
[0086] In the above-mentioned physical foaming, it is preferable
that carbonic acid gas or nitrogen gas in a supercritical state be
injected into the molten resin material because a large number of
fine foam cells having the average cell diameter of less than 400
.mu.m, preferably 200 .mu.m or less can be reliably foamed.
[0087] Here, the term "supercritical state" refers to a state where
the density of a gas and a liquid becomes equal so that the gas and
liquid cannot distinguishably exist, due to exceeding of the
limiting temperature and the limiting pressure at which both the
gas and the liquid can coexist. The fluid produced in this
supercritical state is called a supercritical fluid. In addition
the temperature and the pressure in a supercritical state are
respectively called a supercritical temperature and a supercritical
pressure. For example, for carbonic acid gas the supercritical
temperature is 31.degree. C. while the supercritical pressure is
7.4 MPa. Further, carbonic acid gas or nitrogen gas in the
supercritical state may be injected in an amount of about 4 to 15
mass % with respect to the resin material. It can be injected into
the molten resin material in a cylinder.
[0088] The shape of the extruded foam may be any known shape of
structural materials including a plate, a cylinder, a rectangle, a
convex, and a concave shape, but not specifically limited
thereto.
[0089] Further, the extruded foam may be formed as an assembly of
bundled threads of extruded foam. The assembly is formed such that
a plurality of threads are extrusion-foamed from the extrusion die
in which a plurality of extrusion orifices are formed to be fused
and bundled together in the longitudinal direction. By bundling the
plurality of threads of the extruded foam to be the assembly of the
bundled threads of the extruded foam, the expansion ratio of the
extruded foam can be increased. Thus, the foam-molded product
having a high expansion ratio and a sufficient thickness can be
easily molded into various shapes.
[0090] Note that the production of such an assembly of a bundle
threads of extruded foam is known in the art and it is disclosed
not only for example, in Patent Documents 1 and 2 described above,
but also in JP 53-1262 A, and the like.
[0091] The shape of the thread which constitutes the assembly of
the bundled threads of the extruded foam depends on the shape of
the extrusion orifice formed in the extrusion die. The extrusion
orifice may have a desirable shape. Examples thereof include a
circle, a rhombus, and a slit. In molding, the pressure loss at the
outlet portion of the extrusion die is preferably 3 MPa to 50
MPa.
[0092] In addition, all the extrusion orifices formed in the
extrusion die may be of the same shape, or each of the extrusion
orifices may have a different shape such that orifices of various
shapes can be formed in one extrusion die.
[0093] Further, for example, even when the extrusion orifices are
formed in a shape of circle, all the orifices do not need to have
the same circle diameter, and the plurality of orifices each may
have a different diameter.
[0094] The extruded propylene-based resin foam of the present
invention thus obtained has the expansion ratio of 10 or more and
the average cell diameter of less than 400 .mu.m, so that the air
bubble wall can be formed in plurality in the extruded foam.
Therefore, a radiation heat from the outside can be effectively
blocked and the extruded foam having the excellent insulation
efficiency can be provided.
[0095] Further, the average cell diameter of the extruded
propylene-based resin foam is preferably 200 .mu.m or less. When
the average cell diameter is further smaller to be 200 .mu.m or
less, more air bubble walls can be formed in the extruded foam.
Therefore, the extruded propylene-based foam having an improved
insulation efficiency is provided.
[0096] The propylene-based resin as the constituent material
contained in the extruded propylene-based resin foam of the present
invention is also excellent in recycling performance. In addition,
it has good chemical resistance and heat-resisting property.
Accordingly, the extruded propylene-based resin foam of the present
invention is to be provided with those properties (i.e., recycling
performance, chemical resistance, and heat-resisting property).
Further, the use of the propylene-based resin, which is a low-cost
material, can realize the provision of the extruded foam having the
above-mentioned effects at a low cost.
[0097] The extruded foam of the present invention is excellent in
insulation efficiency as described above, so the extruded foam can
be used for a structural material (a component of a ceiling, a
door, a floor, a cowl, or the like) in the field of automobiles,
and a structural material (for example, a building material) in the
fields of building construction and civil engineering.
[0098] Further, since the extruded foam of the present invention
has the average cell diameter as small as less than 400 .mu.m
(preferably 200 .mu.m or less), the extruded foam can be provided
with an excellent insulation efficiency. When compared with a
conventional extruded foam that has the same level of the
insulation efficiency, the extruded foam is also advantageous
because it can be formed thinner than the conventional foam while
maintaining the level of the insulation efficiency. Therefore, for
example when the present invention is applied to the fields as
described above the extruded foam of the present invention can
favorably provide an additional advantage that with the use of the
present invention the larger living space can be obtained than with
the use of the conventional thermal insulation material.
[0099] Note that the embodiment as described above merely
represents an example of embodiments of the present invention and
the present invention is not limited to the above embodiment. As a
matter of course, the modification and improvement to the
configuration without departing from the objects and advantages of
the present invention shall be included in the scope of the present
invention. The specific structure, shape, and the like in embodying
the present invention may be any other structure, shape, and the
like as long as it does not depart from the objects and advantages
of the present invention.
BRIEF DESCRIPTION OF DRAWINGS
[0100] FIG. 1 is an electron micrograph of the cross section of an
extruded propylene-based resin foam (assembly of bundled threads of
extruded foam) obtained in Example 1 (a magnification of 50).
EXAMPLES
[0101] The present invention will be described below in more detail
with reference to examples and production examples. However, the
present invention is not limited to the contents of the examples or
the like.
[0102] Note that numerical values of solid properties and the like
in the examples and the production examples described below were
measured by the methods described below.
[0103] (1) Mass fractions of a propylene-based polymer component
(Component 1) at the first stage and a propylene-based polymer
component (Component 2) at the second stage:
[0104] The mass fractions were obtained from the mass balance using
the flow meter integrated value of propylene continuously supplied
at the time of polymerization.
[0105] (2) Intrinsic viscosity [.eta.]:
[0106] The intrinsic viscosity [.eta.] was measured in a tetralin
solvent at 135.degree. C. Further, the intrinsic viscosity
[.eta..sub.2] of Component 2 was calculated by the following
expression (II):
[0107] [Formula 3]
[.eta.]=([.eta..sub.total].times.100-[.eta..sub.1].times.W.sub.1)/W.sub.-
2 (II)
[0108] [.eta..sub.total]: Intrinsic viscosity (dL/g) of the entire
propylene-based polymer
[0109] [.eta..sub.1]: intrinsic viscosity (dL/g) of Component 1
[0110] W.sub.1: Mass fraction (mass %) of Component 1
[0111] W.sub.2: Mass fraction (mass %) of Component 2
[0112] (3) Melt flow rate (MFR):
[0113] MFR was measured based on JIS K7210 at a temperature of
230.degree. C. and a weight of 2.16 kgf.
[0114] (4) Melt tension (MT):
[0115] Capirograph 1C (manufactured by Toyo Seiki Seisaku-sho.
Ltd.) was used and measured at a measurement temperature of
230.degree. C. an extrusion rate of 10 mm/min, a drawing
temperature of 3.1 m/min. For the measurement, an orifice having a
length of 8 mm and a diameter of 2.095 mm was used.
[0116] (5) Measurement of viscoelasticity:
[0117] The viscoelasticity was measured using a device having the
following specifications. In addition, the storage modulus G' was
obtainable from a real number part of the complex modulus.
[0118] Device: RMS-800 (manufactured by Rheometrics, Co., Ltd.)
[0119] Temperature: 190.degree. C.
[0120] Distortion: 30%
[0121] Frequency: 100 rad/s to 0.01 rad/s
Production Example 1
Production of Propylene-Based Multistage Polymer
(i) Preparation of Pre-Polymerization-Catalyst Component:
[0122] After a three-necked flask of 5-liter inner volume equipped
with a stirrer underwent treatments of sufficient drying and
nitrogen gas substitution, 4 liters of dehydrated heptane and 140
grams of diethyl aluminum chloride were added thereinto. Then, 20
grams of commercially-available Solvay titanium trichloride
catalyst (manufactured by Tosoh Finechem Corporation) was added.
Thereafter, propylene was continuously added into the flask in
which a stirring operation was being performed with the temperature
maintained at 20.degree. C. After 80 minutes, the stirring was
terminated. Consequently, a pre-polymerization catalyst component
was produced in which 0.8 g of propylene was polymerized per gram
of titanium trichloride catalyst.
(ii) Polymerization of Propylene (1st Stage)
[0123] After a stainless autoclave of 10-liter inner volume
equipped with a stirrer underwent treatments of sufficient drying
and nitrogen gas substitution, 6 liters of dehydrated heptane was
added and the nitrogen in the system was replaced with propylene.
Thereafter, propylene was added into the autoclave in which a
stirring operation was being performed. The inside of the system
was then stabilized at an inner temperature of 60.degree. C. and a
total pressure of 0.78 MPa. Subsequently, 50 milliliters of heptane
slurry was added into the autoclave, the heptane slurry containing
the pre-polymerization catalyst component obtained in the
above-mentioned (i) at an amount equivalent to 0.75 grams of the
solid catalyst, thereby initiating a polymerization. The yield of
the polymer, which was calculated from the integrated value of
propylene flow when the propylene was continuously supplied for 35
minutes, was 151 grams. Sampling and analyzing of a part of the
polymer proved that the intrinsic viscosity was 14.1 dL/g. After
that, the inner temperature was lowered to 40.degree. C. or less,
the stirring was slowed down, and the pressure was released
(iii) Polymerization of Propylene (2nd Stage)
[0124] After the pressure is released, the inner temperature was
again increased to 60.degree. C. and 0.15 MPa of hydrogen was added
into the autoclave. Propylene was added thereto while a stirring
operation was being performed. Continuously added at a total
pressure of 0.78 MPa, the propylene had been polymerized at
60.degree. C. for 2.8 hours. At this time, a part of the polymer
was sampled and analyzed, and the intrinsic viscosity was 1.16
dL/g.
[0125] After the completion of the polymerization, 50 milliliters
of methanol was added to the polymer, then the temperature was
lowered and the pressure was released. The total contents were
transferred to a filtering tank equipped with a filter to add 100
milliliters of 1-butanol, and then the contents were stirred at
85.degree. C. for 1 hour for solid-liquid separation. Further, a
solid part was washed two times with 6 liters of heptane at
85.degree. C. and dried under vacuum thereby providing 3.1 kg of a
propylene-based polymer.
[0126] From the above-mentioned result, a polymerization weight
ratio of the first stage to the second stage was 12.2/87.8. The
intrinsic viscosity of the propylene-based polymer component
generated at the second stage was calculated as 1.08 dL/g.
[0127] Subsequently, 600 ppm of IRGATOX 1010 (manufactured by Ciba
Specialty Chemicals, Co., Ltd.) as an antioxidant and 500 ppm of
calcium stearate as a neutralizing agent were added to be mixed
therewith in relation to 100 parts by weight of powder of the thus
obtained propylene-based multistage polymer. The mixture thereof
was melt-mixed by Labo-Plastomill mono-axial extruder (manufactured
by Toyo Seiki Seisaku-sho Ltd., 20 mm in diameter) at a temperature
of 230.degree. C. to form a propylene-based pellet. The solid
property and resin characteristics of the resultant propylene-based
multistage polymer are shown in Table 1.
[0128] (Solid Property and Resin Characteristics of Propylene-Based
Multistage Polymer)
TABLE-US-00001 TABLE 1 Production Example 1 Propylene-based polymer
Intrinsic viscosity (dL/g) 14.1 component at 1st stage Weight
fraction (mass %) 12.2 Propylene-based polymer Intrinsic viscosity
(dL/g) 1.08 component at 2nd stage Weight fraction (mass %) 87.8
Propylene-based polymer Intrinsic viscosity (dL/g) 2.67 (pellet
form) MFR (g/10 minutes) 3.3 MT (g) 7.6 Viscoelastic property
G'(10)/G'(1) 2.68 G'(0.1)/G'(0.01) 2.96
Production Examples 2 to 6
[0129] Production Examples 2 to 6 were produced in processes
similar to those of Production Example 1 as described above. The
Production Examples 2 to 6 are different from the Production
Example 1 in that the respective parts have different
intrinsicviscosities and weight fractions.
[0130] For comparison, Conventional Product 1 general brand for
extrusion: E-105GM) and Conventional Product 2 (general brand for
foam-molding: pf-814) were used, in which neither the first stage
nor the second stage were included.
TABLE-US-00002 TABLE 2 Production Production Production Production
Production Conventional Conventional Sample Example 2 Example 3
Example 4 Example 5 Example 6 product 1 product 2 Propylene-based
Intrinsic viscosity 15 15 8.5 15 8.1 -- -- polymer component (dL/g)
at 1st stage Weight fraction 15 10 16 4.8 11 -- -- (mass %)
Propylene-based Intrinsic viscosity 1.3 1.0 1.3 1.5 1.3 -- --
polymer component (dL/g) at 2nd stage Weight fraction 85 90 84 95.2
89 -- -- (mass %) Propylene-based Intrinsic viscosity 3.36 2.40
2.58 1.97 2.05 3.47 1.73 polymer (dL/g) MFR 2.7 2.65 2.3 11.7 7.9
0.5 2.5 (g/10 minute) MT 6.8 6.1 5.5 1.41 2.3 6.6 -- (g)
[0131] In accordance with the production examples as described
above, an extruded propylene-based resin foam molded product
(assembly of bundled threads of extruded foam) was provided. As the
production method, each of a method using a tandem-type extrusion
foam-molding device (Production Method 1) and a method using a
MuCell injection molding machine (Production Method 2) was
adopted.
Production Method 1
Examples 1 to 3/Comparative Examples 1 and 2
[0132] Propylene-based multistage polymers in pellet for obtained
in Examples 1 to 5 as described above were respectively used as
molding materials. Then, by use of a tandem-type extrusion
foam-molding device disclosed in JP 2004-237729A (having two mono
axial extruders: a monoaxial extruder having a screw diameter of
.phi.50 mm and the other monoaxial extruder having a screw diameter
of .phi.35 mm) and an assembly of a plurality of circular extrusion
orifices (cylindrical dies) as a die, extruded propylene-based
resin foam as a plate-shaped assembly of bundled threads of
extruded foam was produced in the method as described below. In the
produced extruded propylene-based resin foam, a plurality of
extrusion-foamed threads were bundled together.
[0133] Note that the foaming was performed using a 50-mm-diameter
monoaxial extruder by an injection of a CO.sub.2-supercritical
fluid.
[0134] Specifically, while the molding material was being melted
using the 50-mm-diameter monoaxial extruder, the
CO.sub.2-supercritical fluid was injected. After the fluid was
uniformly and sufficiently dissolved in the molten molding
material, the material was extruded from the 35-mm-diameter
monoaxial extruder connected thereto such that a resin temperature
became 180.degree. C. at the die-outlet of the extruder to mold
extruded foam. The details of the conditions of the production are
described below.
[0135] Note that as the resin temperature at the die-outlet of the
35-mm-diameter-monoaxial extruder, for example, a value obtained by
measurement using a thermocouple thermometer may be adopted. The
resin temperature may be considered to correspond to the
temperature of a foaming molten resin when extruded.
[0136] (Production Condition)
[0137] CO.sub.2-supercritical fluid: 7 mass %
[0138] Extrusion amount: 8 kg/hr
[0139] Resin pressure at upstream of die: 8 MPa
[0140] Extrusion temperature at outlet of die: 180.degree. C.
[0141] The expansion ratio, the average cell diameter, and the
closed cell content of the thus-obtained extruded propylene-based
resin foam were respectively 31, 110 .mu.m, and 60% when measured
under the following conditions.
[0142] (Measurement Conditions)
[0143] Expansion ratio: The weight of the molded foam product
obtained was divided by the volume thereof defined by a submerging
method to obtain a density, and the expansion ratio was then
calculated.
[0144] Average cell diameter: It was measured based on ASTM
D3576-3577.
[0145] Closed cell content: It was measured based on ASTM
D2856.
[0146] Thermal conductivity: It was evaluated based on JIS
A1412
[0147] (Test Results)
[0148] FIG. 1 is an electron micrograph of the cross section of the
extruded propylene-based resin foam obtained in Example 1
(Magnification of 50).
[0149] According to FIG. 1, a large number of foam cells having an
average cell diameter of less than 400 .mu.m are confirmed to be
uniformly arranged on the extruded propylene-based resin foam
obtained in Example 1.
[0150] For the state of foaming, the results shown in Table 3 were
obtained
TABLE-US-00003 TABLE 3 Comparative Comparative Example 1 Example 2
Example 3 Example 1 Example 2 Molding material Production
Production Production Production Production Example 1 Example 2
Example 3 Example 4 Example 5 Expansion ratio 31.0 32.2 31.1 28.4
21.3 Average cell diameter 110 167 185 281 248 Closed cell content
60 65.6 65.8 31.6 3.8
[0151] The molded products from Production Examples 1 to 3 attained
sufficient closed cell content and could be qualified to be
respectively Examples 1 to 3 of the present invention. However, the
products from Production Examples 4 and 5 did not attain sufficient
closed cell content, therefore they were referred as Comparative
Examples 1 and 2.
[0152] With the thermal conductivity of 0.036 W/mk thus attained,
it could be confirmed that the extruded foam of the present
invention had an excellent insulation efficiency or heat-resisting
property.
Production Method 2
Examples 4 and 5/Comparative Examples 3 to 6
[0153] Polypropylene-based multistage polymers of Production
Examples 1 to 4 and 6 and Conventional Products 1 and 2 were used
as molding materials and simply foamed using a MuCell injection
molding machine. Then, test pieces were cut out of the molded
product.
(Production Conditions)
[0154] Molding machine: J180 EL-MuCell manufactured by Japan Steel
Works, Ltd.
[0155] Injected time: 5 seconds
[0156] Injection resin amount: 100 g
[0157] Cylinder preset temperature: 180.degree. C.
[0158] Foaming agent: CO.sub.2-supercritical fluid
[0159] Gas volume: 5 wt %
(Test Results)
[0160] Results were obtained with respect to the state of air
bubbles, as shown in Table 4.
TABLE-US-00004 TABLE 4 Comparative Comparative Comparative
Comparative Example 4 Example 5 Example 3 Example 4 Example 5
Example 6 Molding material Production Production Production
Production Conventional Conventional Example 2 Example 3 Example 4
Example 6 Product 1 Product 2 Expansion ratio 24.0 25.4 18.4 16.9 5
12 Average cell 100 102 170 207 -- -- diameter Closed cell 62.1
63.2 25.2 5.3 -- -- content Foam moldability .largecircle.
.largecircle. .largecircle. .largecircle. .largecircle. X
[0161] The molded products from Production Examples 2 and 3 had
sufficient closed cell content and qualified to be respectively
Examples 4 and 5 of the present invention. However, the molded
products from Production Examples 4 and 6 and Conventional Products
1 and 2 had insufficient closed cell content and thus referred to
as Comparative Examples 3 to 6.
[0162] Evaluation of foam moldability was performed as follows:
[0163] At the time of molding a thread-shaped extruded foam, when
it was confirmed that a protrusion was stable and variations in
cell diameter and expansion ratio were small, the product was
determined to be stable (mark .largecircle.). Likewise, when not
stable, the product was determined to be unstable (mark X).
[0164] [Relation Between Results of Production Method 1 and
Production Method 2]
[0165] According to Production Method 2 as described above, it is
possible to evaluate by sampling a small amount (2 to 3 kg). If a
relation between the experimental results of Production Method 2
and the results of the actual extrusion-foaming test is confirmed
it becomes possible to evaluate the extrusion foaming properties by
sampling a small amount as in Production Method 2. Thus, a relation
between the foam moldability evaluated in the above tandem-type
extrusion foam-molding device (Production Method 1) and the foam
moldability evaluated in Production Method 2 was examined. For
Production Examples 2 to 4, experiments were performed in
accordance with both Production Method 1 and Production Method 2.
As a result, as long as the foaming property was good (high
expansion ratio, fine cell) in Production Method 1, it could be
confirmed that foaming property was also good in Production Method
2. Therefore, the foam moldability in the general extrusion
foam-molding process was confirmed to be evaluable using Production
Method 2.
INDUSTRIAL APPLICABILITY
[0166] The extruded propylene-based resin foam according to the
present invention can be advantageously used for structural
materials that require insulation efficiencies in the fields of,
for example, building construction, civil engineering and the
fields of automobiles.
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